Terahertz　(THz)　technology　has　firmly　established　itself　as　an　effective　sensing　and　nondestructive　testing　(NDT)　technique　for　the　detection　of　substances　and　physicochemical　evaluation　of　materials　and　structural　systems　since　its　first　emergence　almost　three　decades　ago.　To　date,　both　the　effectiveness　and　accuracy　of　this　technology　have　been　extensively　demonstrated　in　a　myriad　of　applications　across　the　spectrum　of　research　and　development　all　the　way　to　process　analytical　technology　(PAT),　quality　control,　NDT,　and　structural　health　monitoring.　These　applications　are　generally　enabled　by　the　production　and　availability　of　advanced,　versatile,　robust,　highly　accurate,　and　industrially　rugged　THz　spectroscopy　and　imaging　(THz-SI)　systems,　the　unique　properties　of　THz　waves　compared　with　other　electromagnetic　waves,　as　well　as　the　advancements　in　electronics,　photonics,　and　THz　metamaterial　systems　development.　This　article　presents　a　comprehensive　state-of-the-art　and　state-of-the-practice　review　of　sensing　and　NDT　applications　of　THz　technology　and　analyzes　the　role　of　THz　metamaterials　in　enhancing　the　resolution　and　sensitivity　of　THz　systems.　The　study　also　provides　a　general　overview　of　the　fundamentals　of　THz-SI　systems　and　discusses　the　suitability　of　THz　sensing　and　NDT　in　a　variety　of　real-world　application　scenarios　(e.g.,　composites＇　defect　detection　and　evaluation,　paints　and　coatings　thickness　measurement　and　characterization,　and　biomolecule　detection).　Aspects,　such　as　the　noise　caused　by　the　presence　of　barriers,　challenges　with　experimental　implementations　and　operability　of　THz　systems,　long　times　required　to　acquire　THz　images,　as　well　as　limited　customizability　and　portability　of　currently　available　THz　systems,　are　also　discussed.　©　2023　IEEE.